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Beebe 

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Having a well-rounded knowledge of the materials that you are using can be a good in itself -
Insulating materials such as Celotex come with specific detailing instructions when used in the walls of the houses we live in. They are conventionally used in combination with a vapour barrier on the warm side (taping joints achieves the same) and a relatively wide, still air-space on the cold side. So, in order to get maximum benefit, we would put the insulation inside the walls of the hive but separated from the timber by a 50mm gap. Then the whole hive would need to be wrapped with a semi-permeable membrane so that the wood could "breathe".

What a faff all that would be! I think the "compromise" of making cosies out of PIR board or from waterproof, wrapped insulation which isn't rigid, and fixing that up, close to the hive body, is a good use of materials and we now have plenty of user-evidence that it reliably achieves the main objective.....if that objective is the successful wintering of bees. :)
 

Erichalfbee 

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Insulating materials such as Celotex come with specific detailing instructions when used in the walls of the houses we live in. They are conventionally used in combination with a vapour barrier on the warm side (taping joints achieves the same) and a relatively wide, still air-space on the cold side. So, in order to get maximum benefit, we would put the insulation inside the walls of the hive but separated from the timber by a 50mm gap. Then the whole hive would need to be wrapped with a semi-permeable membrane so that the wood could "breathe".

What a faff all that would be! I think the "compromise" of making cosies out of PIR board or from waterproof, wrapped insulation which isn't rigid, and fixing that up, close to the hive body, is a good use of materials and we now have plenty of user-evidence that it reliably achieves the main objective.....if that objective is the successful wintering of bees. :)
Mine
CFF60988-7213-42DE-B510-6CD97E9587B8.jpeg
 

Lottie 

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Doing some of those sims, you can really see the different insulation makes.

View attachment 24973

Here you can see both Thermafleece (wool) and Celotex (PIR) are both good insulators. They stop the heat moving out with any rapidity. Let's compare that with 20mm wood (about the thickness of your average hive wall, roof may vary)

View attachment 24974
Oof. You can see that the wood is letting a lot of heat through quite rapidly, with the space between the heat source and the barrier (the wood) fluctuating quite a bit. Compare that to the nice and uniformly toasty space under the PIR board. Now let's model the worse-case scenario: you have vents in your roof space providing direct access to the outside air and only the coverboard between your bees and that environment. Let's say it's a Thorne's 6mm birch ply cover.

View attachment 24975

Yikes. You're losing heat so fast that areas under the coverboard are going cold and you can actually see a plume of heated air escaping after being conducted through the plywood. Quick checks with the thermometer show that for every 30 degrees of heat your bees generate, you're losing 21 degrees of that. 70% of the energy your bees are using is being wasted. Compare this to 5 degrees for the 50mm of PIR board, where they are only losing 20%. That's quite a substantial difference. In a world of spherical cows, you could even argue that the insulated bees are going to eat a third of the stores compared to the uninsulated bees.
Why do they still make vented roofs then? It seems unnecessary in winter. What about summer? It does get hot under a metal roof.
 

jenkinsbrynmair 

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Why do they still make vented roofs then?
Because manufacturers still pander for the dinosaurs who follow a mantra that has never been correct, let alone sensible. Vents in roofs serve no purpose it's only the UK who still insist on having them
 

gmonag 

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Why do they still make vented roofs then? It seems unnecessary in winter. What about summer? It does get hot under a metal roof.
I made some nuc roofs without vents. After about a couple of weeks' use with a rapid feeder on, I found black mould inside the roof. So I cut vents, no more mould.
 

Erichalfbee 

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I made some nuc roofs without vents. After about a couple of weeks' use with a rapid feeder on, I found black mould inside the roof. So I cut vents, no more mould.
Yes it comes down to insulation again. Poly roofs have no vents and they don’t suffer with mould neither do my wooden roofs with celotex glued in.
 

Sayle 

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So they do :)
They are painted green now
I like your entrances, too! Following the 15cm rule by the looks of it.

Why do they still make vented roofs then? It seems unnecessary in winter. What about summer? It does get hot under a metal roof.
Because people with the mantra of 'damp kills bees' want them, so manufacturers provide. Of course these are manufacturers who don't necessarily keep bees themselves or even know certain properties of their hives. I inquired with Abelo as to what the k-value of their hive material was. Their answer? They don't know, because they get it from Poland. The company which sells its hives with a major part of their sales pitch being that the hive is well-insulated and so warmer in winter and cooler in summer don't know how insulated they actually are. It boggles the mind.
 

Erichalfbee 

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I like your entrances, too! Following the 15cm rule by the looks of it.
I kept them like that all year but all the floors are Under Floor Entrance now
 

Murox 

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Insulating materials such as Celotex come with specific detailing instructions when used in the walls of the houses we live in. They are conventionally used in combination with a vapour barrier on the warm side (taping joints achieves the same) and a relatively wide, still air-space on the cold side. So, in order to get maximum benefit, we would put the insulation inside the walls of the hive but separated from the timber by a 50mm gap. Then the whole hive would need to be wrapped with a semi-permeable membrane so that the wood could "breathe".

What a faff all that would be! I think the "compromise" of making cosies out of PIR board or from waterproof, wrapped insulation which isn't rigid, and fixing that up, close to the hive body, is a good use of materials and we now have plenty of user-evidence that it reliably achieves the main objective.....if that objective is the successful wintering of bees. :)
That is pretty much how I build my long deep hives. Not really that much of a faff, especially when most of the materials are leftovers/scrap bits from jobs/skips.
 

Beebe 

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That is pretty much how I build my long deep hives. Not really that much of a faff, especially when most of the materials are leftovers/scrap bits from jobs/skips.

Luxury. :)
 

Antipodes 

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Why do they still make vented roofs then? It seems unnecessary in winter. What about summer? It does get hot under a metal roof.
Here, the holes are for ventilation when moving bees. They are called Langstroth migratory lids. The holes (usually 4), are not generally blocked after the move....they just stay open. I use a travel screen mesh instead when moving them, so there is usually no need for me to have the holes. I tape them up if my lids are made with them. The lids are usually covered in metal and are painted white.
 

Popparand 

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My hive roofs all came with neat meshed ventilation slots. After insulating these were effectively covered over and so inoperative. My floors are omf and I always leave the boards in so I can check what's going on in the hive. I have never had condensation problems so have no reason to change....
 

oliver90owner 

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My hive roofs all came with neat meshed ventilation slots.

Timber roofs need ventilation. This has nothing at all to do with gaping holes in crown boards.

Timber can rot if damp gets in; ventilation allows any moisture above the crown board to escape. In summer,an air flow over the crown board may help to cool the heat conducted through the roof.

Anyone got a polyhive with roof ‘ventilators’? Thought not.
 

Gilberdyke John 

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My hive roofs all came with neat meshed ventilation slots.

Timber roofs need ventilation. This has nothing at all to do with gaping holes in crown boards.

Timber can rot if damp gets in; ventilation allows any moisture above the crown board to escape. In summer,an air flow over the crown board may help to cool the heat conducted through the roof.

Anyone got a polyhive with roof ‘ventilators’? Thought not.
There's a ventilator hole in the new version Abelo roof. Needless to say the solid plug is wedged in the one I have.
 

Beebe 

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There's a ventilator hole in the new version Abelo roof. Needless to say the solid plug is wedged in the one I have.
I think there's several vent holes...maybe four. I was thinking that in combination with the optional vent holes in the crownboard, you can arrange excellent ventilation when it is needed, for example, when transporting a hive in summer. Despite some detractors, the more I get into beekeeping, the more I value these optional features of the Abelo.
 

jenkinsbrynmair 

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Timber roofs need ventilation.
No they don't - none of my timber roofs (and I have quite a few) have vents in, none have any rot.
But then, I'm not foolish enough to fix battens around the edges leaving a 3/4" gap or leave gaping holes in my crownboard - or matchsticks under them
 

Sayle 

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My hive roofs all came with neat meshed ventilation slots.

Timber roofs need ventilation. This has nothing at all to do with gaping holes in crown boards.

Timber can rot if damp gets in; ventilation allows any moisture above the crown board to escape.
No, timber roofs do not need ventilation. Is your loft ventilated? If your timber is rotting from the piddly moisture that escapes from the inside of the hive then only one thing is true, and that's that you haven't properly protected the wood. Either get a hive made from a wood that doesn't need treating (something with natural oils, ie western red), or treat it with a simple water-based polyurethane varnish.

In summer,an air flow over the crown board may help to cool the heat conducted through the roof.
The heat conducted through a hot roof is negligible compared to the effect of outside air temperature and the normal heat production of the hive. If the bees don't like it they have a perfectly normal way of regulating the internal temperature - either pushing hot air out through the entrance or by bearding. Or you could insulate and keep them cool in summer that way, if you're so worried about the possibility that you'd rather sabotage them in winter with roof vents.

Anyone got a polyhive with roof ‘ventilators’? Thought not.
Even a casual look through available polyhives will show that some of the most popular brands (like Abelo) offer roof ventilation.

So...wrong, wrong, wrong.
 

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